1. Field Of The Invention
This invention relates to a fire retardant, and in particular to a fire retardant useful as a coating for cellulosic materials and for admixture with hydrocarbons.
2. Brief Statement Of The Prior Art
Oxygenated boron compounds such as borax (sodium tetraborate decahydrate) and boric acid are known to impart fire retardancy to cellulosic materials, particularly when admixed with other agents. U.S. Pat. No. 641,801 discloses that a mixture of borax, magnesium sulfate, gypsum and ammonium chloride is a fire retardant for fabric when used at concentrations of about 10 weight percent.
U.S. Pat. No. 3,378,381 discloses that wood can be made fire retardant by impregnation at elevated temperatures and pressures with a mixture of borax, boric acid and lignin sulfate and wax at concentrations of about 10 weight percent.
U.S. Pat. No. 3,438,847 discloses that a fire retardant composite board can be prepared by soaking wood chips in a solution of disodium metaborate, drying the chips and then treating the dried chips with boric acid and a resin and wax mixture. The metaborate and boric acid are used at concentrations of 20-29 weight percent of the wood chips.
U.S. Pat. No. 4,184,969 discloses cellulose fiber insulation which is impregnated with 12 to 18 weight percent of a mixture of alumina trihydrate, ammonium sulfate, borax, boric acid and nepheline syenite (a sodium potassium alumina silicate).
U.S. Pat. No. 4,224,169 discloses that a mixture of ammonium bromide and iodide, ammonium orthophosphate, borax, boric acid, ammonium sulfate and sodium silicate can be used as a fire retardant coating.
U.S. Pat. No. 4,461,721 discloses that a mixture of boric acid and an alkanol amine such as monoethanol amine can be used to impregnate wood and impart fire retardancy. The amine is used to facilitate the penetration of the wood by boric acid.
The prior art which has thus used oxygenated boron compounds as fire retardants at relatively high dosages, typically about 10 weight percent or greater, on cellulosic materials such as wood and cellulosic fabrics. Additionally, the prior art has admixed other fire retardants such as ammonium halides and inorganic oxides such as alumina and alumina silicates with boron compounds to achieve desired fire retardancy. This approach is not entirely satisfactory because it imparts toxicity to the retardant and treated substrate and because the decomposition products from exposure to a flame are toxic, e.g., hydrogen iodide and iodates or bromide or bromates. Further, the inorganic oxides increase the solids loading of the treating solution, impairing the clarity of coatings and inhibiting the penetration of the retardants into the substrate.